I have never shot at a 3D target, but then I don't aim for the heart on a live animal either. I am a lung shooter, and it has worked well for me. On angled shots, aim for the apposite side front leg, if you hit that leg, you will take out vitals. If on enough of an angle you will get liver and at least one lung (some guts just because of angle). On broadside shots, I aim just behind the front shoulder dead center. After you have done it a few times it becomes instinctive and you just shoot.
So I practice on a 4' x 4' target with blaze orange duct tape spots, deer don't have them that I have seen but it works.
Ches.